1. Technical Field of the Invention
The present invention relates to a method for manufacturing piezoelectric elements used for droplet-ejecting recording heads, nonvolatile semiconductor storage, thin-film capacitors, sensors, surface acoustic wave elements, filters, surface acoustic wave light guides, optical memories, spatial light modulators, and the like and also relates to a piezoelectric element and a droplet-ejecting recording head.
2. Description of the Related Art
In general, conventional piezoelectric elements include an upper and a lower electrode and a polycrystalline piezoelectric thin-film disposed therebetween. The piezoelectric thin-film is generally classified into a two-component system or a three-component system depending on the composition, wherein the two-component system mainly contains lead zirconate titanate, hereinafter referred to as PZT, and the three-component system contains a third component in addition to the PZT of the two-component system. The piezoelectric thin-film having such composition can be formed by a sputtering method, a sol-gel method, a laser-ablation method, a CVD method, and the like.
When the piezoelectric elements are used for droplet-ejecting recording heads, the piezoelectric elements must include a piezoelectric thin-film that has a thickness of 0.5 to 20 μm. This piezoelectric thin-film must further have a large coefficient of piezoelectric strain.
On the other hand, the upper and lower electrodes of the piezoelectric element contain a conductive material such as platinum, iridium, ruthenium, titanium, gold, and nickel.
Recently, various droplet-ejecting recording heads including the above-mentioned piezoelectric elements have been proposed. In conventional methods for manufacturing the piezoelectric elements, the upper electrode is formed as follows: the lower electrode and the piezoelectric thin-film are formed over a substrate in that order, the upper electrode is provided over the piezoelectric thin-film using platinum by a sputtering method, the resulting upper electrode is then etched to remove unnecessary portions together with the piezoelectric thin-film by a photolithographic method; or such a structure is formed by a printing method such as a screen printing method (see, for example, Japanese Unexamined Patent Application Publication No. 5-286131).
However, in the photolithographic method, there is a problem in that the manufacturing cost is high and the tact time is long because the utilization efficiency of raw materials is low and the manufacturing steps are complicated. In the printing method, there is a problem in that the formation of a micro-pattern is difficult, a mask must be prepared for each pattern, and obtained metal layers have high resistance because metal paste for forming the metal layers contains a large amount of binder for increasing the viscosity of the paste. The patterning of the piezoelectric element has the same problem as the above.
Accordingly, in order to solve the above problems, it is an object of the present invention to provide a method for manufacturing a piezoelectric element at low cost in a short tact time, a piezoelectric element, and a droplet-ejecting recording head, wherein the piezoelectric element includes an upper electrode having low resistance.